The present invention relates to an insulating target material suitably used for radio frequency (RF) sputtering, a method of manufacturing the insulating target material, a conductive complex oxide film, and a device.
A target for obtaining a complex oxide film by sputtering is generally obtained as follows. For example, a target for obtaining a perovskite oxide film of the general formula ABO3 is obtained by pulverizing oxide raw materials of the element A and the element B, mixing the oxide raw materials taking the stoichiometric composition into consideration, and sintering the mixture. A material disclosed in JP-A-10-176264 has been known as such a target, for example. This document discloses a sputtering target for a perovskite oxide of the chemical formula ABO3 which has a specific relative density and size.
On the other hand, the inventor of the invention found that a target sufficient for obtaining a conductive complex oxide film of the general formula ABO3 cannot be obtained by merely pulverizing oxide raw materials of the element A and the element B and mixing and sintering the oxide raw materials at a specific composition. For example, the inventor formed a target for forming an LaNiO3 conductive complex oxide film by RF sputtering using a known sintering method to obtain the following findings. Specifically, a target obtained by mixing an La oxide powder and an Ni oxide powder at a composition ratio of 1:1 and sintering the mixture did not exhibit uniform insulating properties over the entire target, in which a portion exhibiting low insulating properties (i.e. portion exhibiting conductivity higher than that of the surrounding portion) was formed. When RF sputtering is performed using such a target, plasma is concentrated on the portion exhibiting low insulating properties, whereby the portion on which the plasma is concentrated may be dissolved or cracks may occur in the target due to plasma concentration. This makes it difficult to use such a target for RF sputtering.